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This Article Full Text Full Text (PDF) All Versions of this Article: 291/5/E1059    most recent 00062.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by López, A. Articles by Tovar, A. R. Search for Related Content PubMed PubMed Citation Articles by López, A. Articles by Tovar, A. R.

Characterization and regulation of the gene expression of amino acid transport system A (SNAT2) in rat mammary gland

¹Departamento de Fisiología de la Nutrición, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; ²Posgrado en Biología Experimental, Universidad Autónoma Metropolitana-Iztapalapa; and ³Departamento de Patología Experimental, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico

Submitted 17 February 2006 ; accepted in final form 10 June 2006

Amino acid transport via system A plays an important role during lactation, promoting the uptake of small neutral amino acids, mainly alanine and glutamine. However, the regulation of gene expression of system A [sodium-coupled neutral amino acid transporter (SNAT)2] in mammary gland has not been studied. The aim of the present work was to understand the possible mechanisms of regulation of SNAT2 in the rat mammary gland. Incubation of gland explants in amino acid-free medium induced the expression of SNAT2, and this response was repressed by the presence of small neutral amino acids or by actinomycin D but not by large neutral or cationic amino acids. The half-life of SNAT2 mRNA was 67 min, indicating a rapid turnover. In addition, SNAT2 expression in the mammary gland was induced by forskolin and PMA, inducers of PKA and PKC signaling pathways, respectively. Inhibitors of PKA and PKC pathways partially prevented the upregulation of SNAT2 mRNA during adaptive regulation. Interestingly, SNAT2 mRNA was induced during pregnancy and to a lesser extent at peak lactation. -Estradiol stimulated the expression of SNAT2 in mammary gland explants; this stimulation was prevented by the estrogen receptor inhibitor ICI-182780. Our findings clearly demonstrated that the SNAT2 gene is regulated by multiple pathways, indicating that the expression of this amino acid transport system is tightly controlled due to its importance for the mammary gland during pregnancy and lactation to prepare the gland for the transport of amino acids during lactation.

system A; mammary gland; amino acid transport; lactation